1971-S Proof Eisenhower Ike Dollar 90% 1 1

[GoldBear150]

This Coin came to my shop a few days back and i tested it with a sigma metalytics verifier. I have it run at 90% percent Because the customer told me it's 90%. and it passed which surprised me a bit. I searched on my red book for more information and only i come across is clad Eisenhower dollars.

[Coinbuf]

I'm not an Ike collector but the proof issues were 40% so how this came up as 90% is a mystery.

[GoldBear150]

Yes 40% is what i expected for this.The customer went to another coin dealer to have it checked out. They did the test and it came out 90% as well after the test they were hesitant of taking it in.

[Modwriter]

Could it be a fake?

[bsshog40]

Doesn't look fake to me so I would have to argue that it is 90% silver. 

[Greenstang]

Don't think it would be a fake, why would someone fake a 90% silver for a 40% silver Ike.

The last time a 90% silver dollar was produced was the 1964 Peace Dollar so that means that somehow a 90% silver planchet from 1964 suddenly appeared in 1971 to produce that Ike. Seems highly unlikely but is there another explanation if that is truly a 90% silver dollar?

[Just Bob]

Like the Kennedy half dollar, Ike silver dollars are clad. The outer layer is 80% silver, 20% copper, over an inner layer of just under 21% silver and 79% copper. My guesses are: either the tester is off a bit, the outer layer composition is off a bit, or the mixture was incomplete, and the tiny spot that the tester read actually was 90%.

Edited to add: For the sake of accuracy, the actual composition of the inner layer is .209 silver and .791 copper.

Edited October 5, 2020 by Just Bob

[DWLange]

Dipping coins in a mild acid solution tends to leech out a bit of the copper alloy, raising the surface percentage of silver. It's hard to say from the photos whether this was done, but it was a familiar tool to minters of old who wanted to increase the perceived value of debased coins.

[VKurtB]

I'd bet anything that it's NOT 90%. Outside layers are 80%.

[RWB]

If the coin was toned, then dipped in an acid solution such as Tarn-X and similar products, some of the silver sulfide (tarnish) would have been converted to the chloride, and some of the surface copper alloy would have been removed. These could easily increase the surface fineness to 0.900 or so.

I really doubt any "coin shop" measurement that is 0.800 or 0.900 on the nose. A trained XRF user who understands instrument calibration and error profile can provide a reliable alloy, but not Joe Schmo in a coin shop of jewelry joint.

Edited October 6, 2020 by RWB

[Conder101]

Weight would be a simple test.  40% silver would weigh 24.59 grams with tolerance up to a maximum weight of 25.57 grams.  A 90% silver coin would weigh 26.73 with a minimum weight of 26.63 grams.  With over a full gram difference between the maximum and minimum weights it should be a pretty reliable test.

Edited October 10, 2020 by Conder101

[Modwriter]

6 minutes ago, Conder101 said:

Weight would be a simple test.  40% silver would weigh 24.59 grams with tolerance up to a maximum weight of 25.57 grams.  A 90% silver coin would weigh 26.73 with a minimum weight of 26.63 grams.  With over a full gram difference between the maximum and minimum weights it should be a pretty reliable test.

Conder! Everybody misses you over at the other TPG.

[GoldBear150]

I weight the coin on my scale. 25.2g.

[RWB]

On 10/10/2020 at 12:18 AM, Conder101 said:

Weight would be a simple test.  40% silver would weigh 24.59 grams with tolerance up to a maximum weight of 25.57 grams.  A 90% silver coin would weigh 26.73 with a minimum weight of 26.63 grams.  With over a full gram difference between the maximum and minimum weights it should be a pretty reliable test.

Almost -- If the outside silver were 0.900 instead of 0.800, and the bulk remained the same calculation indicates a weight increase of just 0.028 grams....well within tolerance.

Clad metal coils for halves and dollars came from the same manufacturer, but were different thicknesses and widths so they could not run through the wrong blank cutters.

26.73 grams applies to a bulk 0.900 silver, 0.100 copper dollar.

Edited October 13, 2020 by RWB